1. Field of the Invention
The invention concerns oil booms that serve as barriers to oil spills and also concerns oil-sorbing sweeps that sorb small quantities of oil from the surface of a body of water. More specifically, the invention concerns the need for a boom that can serve as a barrier to floating oil and can also sorb that oil.
2. Description of the Related Art
An effective technique for the disposal of offshore oil spills is to confine the oil within a floating boom and then remove the confined oil either by pumping or by burn-off. Such a boom is disclosed in coassigned U.S. Pat. No. 4,923,332 (Sanocki et al.) and is currently marketed by 3M Co. as "3M Fire Boom" in 50-foot (15.2-m) lengths. Another fire-resistant boom is disclosed in coassigned U.S. Pat. No. 4,619,553 (Fischer).
Such barrier-type booms are used for disposing of oil spills but are not effective for clearing oil sheen or otherwise keeping water substantially free from oil contamination. Commonly used for that purpose are oil-sorbing sweeps and booms that do not provide barriers to the oil. A typical oil-sorbing sweep consists of a wide oil-sorbing web and a rope sewn along a margin of the web, e.g., the T-126 sweep from 3M Co. Such a sweep can be used in conjunction with a barrier-type boom by being placed downstream from the boom to remove any escaping traces of oil, e.g., to help to keep oil from entering a desalinization plant.
Another oil-sorbing sweep is disclosed in coassigned U.S. Pat. No. 4,052,306 (Schwartz et al.). Its oil-sorbent member preferably is an elongated web of blown microfibers such as polypropylene microfibers reinforced by folding and sewing each of its edges around a rope. Attached to hang freely beneath the floating web is an open-mesh netting that generally is formed from a network of filaments that may be woven, knitted, or fused at their crossing points. The netting can form a "tube" or closed cylinder around the web.
Known oil-sorbing sweeps submerge after becoming saturated with oil, and this causes them to release part of the sorbed oil.
Some oil-sorbing sweeps are called "booms" because they look like the oil-barrier booms even though they are not effective as barriers Typical oil-sorbing booms employ open-mesh bags that are stuffed with oil-sorbing material, e.g., the T-270 and T-280 oil-sorbing boom from 3M Co. Each has an elongated nylon open-mesh bag that is stuffed with oil-sorbent polypropylene blown microfibers. A number of such bags are linked together have the appearance of a chain of sausages.
U.S. Pat. No. 3,679,058 (Smith) shows a sausage-like oil-sorbing sweep (there called a "boom") that is similar to the 3M T-270 and T-280 oil-sorbing booms, but rectangular in shape. It contains "lightweight bats of polymer fibers or blown polymer film of such materials as polypropylene which present enormous fiber surface area on which oil film deposits itself" that are enclosed in a greatly elongated tubular net sleeve that is preferably formed of "lightweight polymer fibers which may be heat-sealed in net configuration or which may be woven or knotted like a fisherman's net" (col. 2, lines 10-40).
In U.S. Pat. No. 3,702,657 (Cunningham et al.), water is allowed to flow through box-shaped cages that are filled with oil-sorbent bags or pads to facilitate disposal of oil on bodies of water and to prevent contamination of shorelines.